1. Field of the Disclosure
The present disclosure relates to an intermittent absorption refrigeration method and an intermittent absorption refrigeration system.
2. Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.
Energy consumption due to air-conditioning and refrigeration applications is significant. The coincidence of maximum cooling loads with the period of highest solar irradiance makes solar energy an excellent candidate for powering refrigeration and air conditioning systems, thereby conserving electrical energy. Absorption chillers have the advantage of being operable even with relatively low-quality heat sources such as exhaust gases from industrial processes or solar radiation. In this regard, absorption chillers have the potential to directly use solar energy to produce refrigeration.
Typical absorption cooling systems utilize a heat source to vaporize under pressure a refrigerant out of a strong solution. The pressurized desorbed refrigerant is then condensed by rejecting heat from it to the ambient environment. The condensed refrigerant is then used for evaporative cooling by evaporating it under lower pressure, whereby ambient heat is absorbed from the refrigerated space. The evaporated refrigerant is then absorbed back into the weak solution, resulting in a rich solution, thereby enabling the process to be repeated.
Absorption chillers are basically classified into two categories: continuous operation systems and intermittent operation systems. The basic difference between continuous and intermittent systems is their mode of operation. In continuous systems, both generation and absorption of the refrigerant take place at the same time in a continuous manner. However, in intermittent systems, generation and absorption do not take place at the same time; rather, they intermittently follow each other with the operation of the system.
Historically, the coefficient of performance of intermittent systems has typically been much lower than that of continuous systems. This is largely because a continuous system is able to employ a recuperator-type solution heat exchanger, wherein hot and cold fluids flowing past one another in adjacent channels exchange thermal energy. In this manner, waste heat generated in one portion of the system can be utilized to provide heat required in another portion of the system, thereby increasing the overall coefficient of performance of the system.
In a typical absorption cooling system, the generation process requires thermal energy to vaporize refrigerant out of a liquid absorbent-refrigerant solution, while on the other hand, the absorption process releases thermal energy as refrigerant vapor is absorbed into absorbent-refrigerant solution. In a continuous absorption system, the generation and absorption processes occur simultaneously, thus, both hot and cold solutions are continuously present during the operation of the system. Since both hot and cold solutions are present, a recuperator-type solution heat exchanger allows the system to recover thermal energy released by the absorption process and to use that recovered energy to help drive the generation process.
For intermittent systems, by contrast, it is not possible to use a recuperator-type heat exchanger for waste energy recovery, since hot and cold solutions are not available at the same time. Thus, the coefficient of performance of intermittent systems has been limited.
On the other hand, an advantage of intermittent systems over continuous systems is that they can be designed to provide a cooling effect without any need of electrical energy for the operation of motors, pumps, and the like. However, achieving practically operable designs for motorless refrigeration systems has involved unacceptable trade-offs in terms of size, complexity, and cost.